Fish health vital for profitable farming

For producers to be able to maintain ideal quality conditions, they must understand the physical and chemical components contributing to good fish production

For producers to be able to maintain ideal quality conditions, they must understand the physical and chemical components contributing to good fish production

The Zimbabwe Fish Producers’ Association, supported by the Zimbabwe Agricultural Society, invites stakeholders in the fish industry and all fish producers to a Workshop and Fish Information Day on December 12, 2017.

This event will be held in the Andy Millar Hall, Exhibition Park from 8:00am and costs $10 per person, inclusive of teas and a hot lunch. Topics include fish health and nutrition as well as an update on the fish industry and aquaculture strategy.

Following the watershed developments in aquaculture over the last two years, Zimbabwe is poised to develop the fish farming potential of the country. Like other livestock, fish will only achieve optimum growth rates when they are thriving and free from stress and disease.

As the country gears up to tap its enormous fish production potential under the Command Fish Programme, it continues to build capacity in the area of fish health and disease surveillance.

Along with other countries in the region, Zimbabwe is monitoring an emerging and potentially decimating fish disease, Tilapia Lake Virus (TiLV), recently reported in Thailand, Israel, North Africa and South America.

Zimbabwe has also just completed a three-year ASTF/FAO regional surveillance programme on Epizootic Ulcerative Syndrome (EUS), a fish disease that has emerged in the last decade. This has identified EUS in six provinces,

Fifteen districts and 25 water bodies in the country. EUS is a fungal agent that causes lesions on the skin of susceptible fish, thereby causing disease and high mortalities in infected fish. Research shows that indigenous fish, the Nile tilapia (Oreochromis niloticus), appear to be resistant to this fungal disease, which can cause widespread losses in other fish species.

The ASTF/FAO programme has also trained extension and research personnel in EUS identification and conducted awareness campaigns for fish farmers and fishermen in affected areas.

A key development in national fish production is the planned establishment of an aquaculture diagnostic laboratory to be housed at the Veterinary Research Laboratory, the centre of livestock diagnostic testing in Zimbabwe. Another aquaculture facility is the fish production demonstration unit at Henderson Research Institute in Mazowe. Fish research is part of the mandate of this national research institute, which also conducts training in aquaculture with a focus on fish health for viable commercial production.

Successful commercial fish production starts with the sourcing of healthy fingerlings from environmentally clean and disease-free stocks. Biosecurity should be practiced, to ensure that fish diseases are not introduced into a fish project from another source.

Maintaining the aquatic environment in a condition that will not compromise fish health or precipitate disease is also critical as it is difficult to isolate diseased fish and contamination is easily spread in an aquatic environment.

Meeting the nutritional requirements of the growing fish and ensuring that they are not subjected to stress are important for optimum health and performance from these aquatic livestock.

At the core of the Code of Practice for aquaculture, being spearheaded by the Zimbabwe Fish Producers’ Association (ZFPA) is fish health. This encompasses aquaculture best practice in production and processing, emphasising health, hygiene and environmental and food safety.

The Aquaculture Code of Practice recognises the Department of Veterinary Services as the national authority in fish disease surveillance and control; and emphasises the importance of environmental stewardship in sustainable commercial fish production.

The importance of good aquaculture practices can be seen when it is realised most bacterial diseases in fish are secondary infections that occur in fish that are under stress from poor water quality, ectoparasites or poor nutrition. Bacteria such as Streptococcus iniae and Flavobacterium can cause mass mortalities on fish farms.

Two fungal diseases affecting fish can be easily prevented. To avoid Saprolegnia a waste or sewage water borne disease, such waste should never be emptied into fish ponds. Aspergillus can develop in mouldy feeds, so only fresh feed should be fed to fish.

Like other livestock, fish can become infected with parasites, some of which are detrimental to fish health and transmissable to humans. The risk of aquatic parasites can be minimised with biosecurity measures.

These include disinfecting equipment, monitoring of water quality and disease, general sanitation of the aquaculture facility and use of protective wear by personnel working at the operation.

Signs that can indicate disease in fish include slow growth rates, lack of response to external stimuli, fish that are not feeding, breathing difficulties and lesions on the skin, as with EUS. Uncharacteristic behaviour of fish, such as gasping, lethargic swimming, spinning, and mortality should also be investigated.

If these signs are evident or disease is suspected for any other reason, advice should be sought from the Department of Veterinary Services and the University of Zimbabwe (Biological Sciences). Both offer diagnostic testing of fish diseases and water quality testing.

Farmers are advised to regularly send water and fish samples to laboratories for testing. A full list of diseases affecting fish in Zimbabwe, infectious, nutritional and environmental, can be obtained from these laboratories.

At all levels, the fish industry is building fish health and disease surveillance capacity, through Veterinary Services support, agricultural extension, information dissemination and other aquaculture support services. Fish health is an integral part of viable fish production, determining the overall productivity and profitability of a fish enterprise.